This invention generally relates to method and apparatus for detecting uneven magnetic field, and more particularly to method and apparatus for electrically detecting the existence of a local inversion of magnetic field such as magnetic bubble domain.
Recently it has been found that a local inversion of magnetic field or magnetic bubble exists in an orthoferrite or garnet element subjected to a bias magnetic field and the art of applying this phenomenon to memory or logic operation has been developed. The conventional method for electrically detecting magnetic bubble domains uses the Hall effect of semiconductor or the magnetic resistive effect of semiconductor or magnetic elements.
As for the prior art of detecting method using the Hall effect of semiconductor, a semiconductor element whose active area is made smaller than the dimensions of the magnetic bubble is conventionally used to detect the magnetic field from the magnetic bubble. In this connection the size of the semiconductor element varies with the size of the magnetic bubble. The semiconductor device to be used for detecting a relatively small magnetic bubble must be accordingly reduced in size, and therefore difficulties arise in producing suitable semiconductor elements. Also, disadvantageously, the detected output signal decreases with the smallness of the element, and accordingly the signal-to-noise ratio decreases. Thus, such small element can not be used for detecting a minute magnetic bubble as small as 5 .mu.m in garnet.
Conventional four-terminal Hall element makes it actually impossible to build a two-dimensional array to detect magnetic bubbles if any, in two dimensional space owing to the complexity of the wiring.
The main object of this invention is to provide a method for detecting uneven magnetic field in which a magnetic field in a given fixed direction and an inverted magnetic field coexist, by using the newly found galvano-magnetic effects of semi-conductor devices.
Another object of this invention is to provide a method for digitally or analogously detecting magnetic bubbles in the magnetic body which method permits the use of a large semiconductor element compared with the magnetic bubble to be detected.
Another object of this invention is to provide an apparatus for detecting uneven magnetic field which apparatus facilitates the building of a two-dimensional array structure.
Another object of this invention is to provide a method for electrically detecting the position of magnetic bubble domains in the magnetic body without shifting the magnetic bubbles.
Another object of this invention is to provide a method for digitally or analogously and simultaneously detecting the position of a plurality of magnetic bubbles.
Another object of this invention is to provide a system to perform logic operations in the course of detecting magnetic bubble domains.